Parkinson's disease is a neurodegenerative disease caused by loss of dopaminergic neural cells in the mesencephalic substantia nigra, and about 4 million people in the world are currently suffering from this disease. For treatment of Parkinson's disease, pharmacotherapy with L-dopa or a dopamine agonist; the coagulation method or deep brain stimulation by stereotaxy; fetal mesencephalic grafting; or the like has been carried out.
Fetal mesencephalic grafting is problematic from an ethical point of view because of its source of supply, and the risk of infection is high in this treatment. Thus, a therapeutic method using neural cells induced from pluripotent stem cells such as embryonic stem cells (ES cells) or induced pluripotent stem cells (iPS cells) has been proposed (Wernig M, et al., Proc Natl Acad Sci USA. 2008, 105: 5856-5861). However, the possibility of formation of a benign tumor after transplantation of induced neural cells has been pointed out, thus, selection of safe cells that can survive has been demanded for the transplantation.
In view of this, genes that can be used as markers for dopaminergic neural cells and/or dopaminergic neuron progenitor cells have been reported (WO2005/052190, WO 2006/009241 and WO 2007/119759), but it is considered that more markers are necessary for restrictive extraction of specific cells suitable for transplantation.